The broad objective is to ask questions of the human brain with well-practiced methods used in ongoing animal studies. We have focused on two separate subjects: (1) Comparative Studies of Sensory Input to Motor Cortex in Animals and Man, and (2) Studies of Presumed Glial Cells (PG cells) in Cat Cerebral Cortex. It is proposed to complete the characterization of the receptive fields and adequate stimuli for motor cortex in raccoon, macaque and man. Also, in man: determine latencies between sensory cue for active hand closure and neuronal firing that precedes the onset of the voluntary movement; compare latencies between the onset of neuronal discharge and movement carried out contralaterally and ipsilaterally to the active cell; use intracortical microstimulation to determine input-output relations; determine effects of isometric contraction to provide information on whether there are muscle afferents projecting to motor cortex. Preliminary findings in the raccoon show that some cells in the S1 hand area can be activated by both ipsilateral and contralateral stimulation. Thus we propose to determine: the laminar and areal distribution of these bilaterally activated cells; the adequate stimuli for their response; interactions of their response to contra and ipsilateral stimuli. For comparison we plan to characterize the quality of input to the S1 hand area of man. Also, to determine the sensory experience prodced by intracortical microstimulation, a question that can be answered uniquely in man. In separate studies we have investigated the effect of various cations on the resting membrane potential of presumed glial cells; also the slow depolarization and ensuing hyperpolarization which PG cells show following direct cortical stimulation. In this proposal we plan to continue with efforts to definitively identify these cells iontophoretically and determine whether they represent a single cell species.